The situation is a major turnaround from last year, when Northern California was battered by a series of "atmospheric river" storms that helped end the state's five-year drought. When it was over, California's northern Sierra Nevada experienced the wettest winter on record, with some ski resorts staying open through the summer.

The dry conditions are partly to blame for the worst fire season on record in California. Low humidity and lack of rain coupled with high winds fueled destructive wildfires from Mendocino down to San Diego this fall. In wine country, more than 40 people died and more than 10,000 homes were lost. To the south, the Thomas fire in Ventura and Santa Barbara counties became the largest wildfire on record in California.

If the trend continues, forecasters say California could see, come spring, a light Sierra Nevada snowpack, a key source of water for the state during the dry summer.

The weather station in California with the longest record of recording rainfall, San Francisco, has measured just 3.4 inches of rain since the start of July. That's only 44 percent of average for this time of year, said meteorologist Jan Null.

So far this December, San Francisco has received only 0.15 inches of rain.

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San Francisco is already close to the halfway point in its rainy season: Jan. 19. In an average year, the city would have received 11.83 inches by then, halfway to the annual average of 23.65 inches, Null said.

Null said he analyzed rain records going back to the oldest precipitation record on file for California, the 1849-50 season in Gold Rush-era San Francisco. He found that there were 22 years in which San Francisco at this point in the season had similar anemic -- but not abysmal -- rainfall, between 2.9 inches and 3.9 inches.

And what Null found was bad news: Of those 22 years, only four of them caught up in the remainder of the rainy season and finished above the average.

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